Asthma mucus hypersecretion

Yuta A, BaraniukJN. Therapeutic approaches to mucus hypersecretion. Curr Allergy Asthma Rep. 2005 5 243-251. 

There is evidence that both occupational and environmental exposures to chemicals (both proteins and haptens) can result in the induction or exacerbation of respiratory allergies (Table 19.6). Of particular concern is the induction of allergic asthma. In sensitized asthmatic individuals the antigen challenge generally causes a type I (IgE-mediated) immediate hypersensitivity response with release of mediators responsible for bronchoconstriction. Between 2 and 8 hours after the immediate response, asthmatics experience a more severe and prolonged (late phase) reaction that is characterized by mucus hypersecretion, bronchoconstriction, airway hyperresponsiveness to a variety of nonspecific stimuli (e.g., histamine, methacholine), and airway inflammation characterized by eosinophils. This later response is not mediated by IgE. 

Whereas asthma is characterised by reversible airways obstruction and bronchial hyperreactivity, COPD is characterised by incompletely reversible airways obstruction and mucus hypersecretion it is predominantly a disease of the smaller airways. Nevertheless, distinguishing the two can be difficult in some patients and one view is that asthma predisposes smokers to COPD (Dutch hypothesis). In practice, even though — indeed precisely because — most of the airway obstruction is fixed in COPD, it is important to maximise the reversible component. This can be assessed by measuring FEVj before and after a course of oral prednisolone, e.g. at least 30 mg/day for 2 weeks reversibility is arbitrarily defined as > 15% rise (and > 200 ml) in... 

The rate of removal of mucus from the airways is determined by such factors as mucus viscosity, the amount of mucus produced, and the degree of ciliary activity. These processes may be influenced by a variety of diseases, including asthma, cystic fibrosis, and chronic bronchitis [82,83], In patients suffering from cystic fibrosis or chronic bronchitis, mucus hypersecretion is evident and mucociliary function is impaired. The failure to clear mucus from the airways leads to airway obstruction and to chronic colonization of the airways with bacterial organisms (which leads to lung infections and airway inflammation and damage). In asthmatic subjects, airway mucus is more viscous and ciliary transport mechanisms are inhibited [82,83]. In these diseases, the therapeutic objective is to improve mucus clearance from the airways. For example, aerosols of water or saline (especially hypertonic saline) promote clearance of mucus by... 

The worldwide incidence, morbidity, and mortality of allergic asthma are increasing. Asthma has become an epidemic, affecting 155 million individuals throughout the world. It is a complex disorder characterized by local and systemic allergic inflammation, mucus hypersecretion, and reversible airway obstruction [88]. The pathogenesis of asthma reflects the activity of cytokines from Th2 cells. Without these cells there is no asthma. Animal models support important roles for the cytokines IL-4, IL-5, and the recent IL-13 [89]. The latter is closely related to IL-4 they both bind to the same IL-4 receptor, to the a-chain of that receptor, particularly. 

Zhu Z, Homer RJ, Wang Z, et al Pulmonary expression of interleukin-13 causes inflammation, mucus hypersecretion, subepithelial fibrosis, physiologic abnormalities, and eotaxin production J Clin Invest 1999, 103 779-788 WiUs-JCarp M, Luyimbazi J, Xu X, et al Interleukin-13 central mediator of allergic asthma [see comments] Science 1998, 282 2258-2261... 

In asthmatic patients, the most common symptoms are dyspnea and bronchospasm than can usually be reversed with bronchodilatation therapy that probably has no effect on mucus clearance transport (20). Hypersecretion is usually present in the acute episodes of asthma and normally mucus transport is impaired due to reduction of ciliary activity (21). Mucus hypersecretion and changes in the rheological or surface properties of mucus may also cause reduction of ciliary activity (6). In these patients, mucus transport can be recovered or remain reduced, despite favorable changes in mucus viscoelasticity after an exacerbation. 

A common complication of persistent hypersecretion and mucus plugging is a less effective mucociliary clearance mechanism. Inhaled bacteria which are normally quickly cleared from the bronchial system have greater opportunity for tissue invasion. Chronically affected asthmatics are more likely to develop bacterial bronchitis. It is not unusual for CB to become superimposed on the asthma as a consequence of these infections. Interestingly asthmatics who get an acute bacterial bronchitis will often note an improvement of their asthmatic symptoms. 

Asthma is a common chronic inflammatory disorder that affects the airway passages of the lungs. Primarily, asthma is characterized by reversible, episodic narrowing of the airway s smooth muscle secondary to hypersecretion of mucus, hyper-reactivity, and mucosal edema. The narrowing may be of sudden or prolonged onset, which accounts for the varying degrees of airway obstruction seen in this disease. The hallmark of airway obstruction is a reduction in the forced expiratory volume in 1 second (FEV and the ratio of FEVj to the forced vital capacity (FVC). 

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